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Panda S, Rout M, Mishra S, Turuk J, Pati S, Dehury B. Molecular docking and MD simulations reveal protease inhibitors block the catalytic residues in Prp8 intein of Aspergillus fumigatus: a potential target for antimycotics. J Biomol Struct Dyn 2023:1-16. [PMID: 38149850 DOI: 10.1080/07391102.2023.2298735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 12/18/2023] [Indexed: 12/28/2023]
Abstract
Resistance to azoles and amphotericin B especially in Aspergillus fumigatus is a growing concern towards the treatment of invasive fungal infection. At this critical juncture, intein splicing would be a productive, and innovative target to establish therapies against resistant strains. Intein splicing is the central event for the activation of host protein, essential for the growth and survival of various microorganisms including A. fumigatus. The splicing process is a four-step protease-like nucleophilic cascade. Thus, we hypothesise that protease inhibitors would successfully halt intein splicing and potentially restrict the growth of the aforementioned pathogen. Using Rosetta Fold and molecular dynamics simulations, we modelled Prp8 intein structure; resembling classic intein fold with horse shoe shaped splicing domain. To fully comprehend the active site of Afu Prp8 intein, C1, T62, H65, H818, N819 from intein sequences and S820, the first C-extein residue are selected. Molecular docking shows that two FDA-approved drugs, i.e. Lufotrelvir and Remdesivir triphosphate efficiently interact with Prp8 intein from the assortment of 212 protease inhibitors. MD simulation portrayed that Prp8 undergoes conformational change upon ligand binding, and inferred the molecular recognition and stability of the docked complexes. Per-residue decomposition analysis confirms the importance of F: block R802, V803, and Q807 binding pocket in intein splicing domain towards recognition of inhibitors, along with active site residues through strong hydrogen bonds and hydrophobic contacts. However, in vitro and in vivo assays are required to confirm the inhibitory action on Prp8 intein splicing; which may pave the way for the development of new antifungals for A. fumigatus.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Sunita Panda
- Mycology Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
| | - Madhusmita Rout
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
| | - Sarbani Mishra
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
| | - Jyotirmayee Turuk
- Mycology Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
| | - Sanghamitra Pati
- Mycology Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
| | - Budheswar Dehury
- Bioinformatics Division, ICMR-Regional Medical Research Centre, Bhubaneswar, India
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Wood DW, Belfort M, Lennon CW. Inteins-mechanism of protein splicing, emerging regulatory roles, and applications in protein engineering. Front Microbiol 2023; 14:1305848. [PMID: 38029209 PMCID: PMC10663303 DOI: 10.3389/fmicb.2023.1305848] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 10/16/2023] [Indexed: 12/01/2023] Open
Abstract
Protein splicing is a posttranslational process in which an intein segment excises itself from two flanking peptides, referred to as exteins. In the native context, protein splicing results in two separate protein products coupled to the activation of the intein-containing host protein. Inteins are generally described as either full-length inteins, mini-inteins or split inteins, which are differentiated by their genetic structure and features. Inteins can also be divided into three classes based on their splicing mechanisms, which differ in the location of conserved residues that mediate the splicing pathway. Although inteins were once thought to be selfish genetic elements, recent evidence suggests that inteins may confer a genetic advantage to their host cells through posttranslational regulation of their host proteins. Finally, the ability of modified inteins to splice and cleave their fused exteins has enabled many new applications in protein science and synthetic biology. In this review, we briefly cover the mechanisms of protein splicing, evidence for some inteins as environmental sensors, and intein-based applications in protein engineering.
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Affiliation(s)
- David W. Wood
- William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, OH, United States
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, NY, United States
| | - Christopher W. Lennon
- Department of Biological Sciences, Murray State University, Murray, KY, United States
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3
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Liu N, Tu J, Huang Y, Yang W, Wang Q, Li Z, Sheng C. Target- and prodrug-based design for fungal diseases and cancer-associated fungal infections. Adv Drug Deliv Rev 2023; 197:114819. [PMID: 37024014 DOI: 10.1016/j.addr.2023.114819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/28/2023] [Accepted: 03/31/2023] [Indexed: 04/07/2023]
Abstract
Invasive fungal infections (IFIs) are emerging as a serious threat to public health and are associated with high incidence and mortality. IFIs also represent a frequent complication in patients with cancer who are undergoing chemotherapy. However, effective and safe antifungal agents remain limited, and the development of severe drug resistance further undermines the efficacy of antifungal therapy. Therefore, there is an urgent need for novel antifungal agents to treat life-threatening fungal diseases, especially those with new mode of action, favorable pharmacokinetic profiles, and anti-resistance activity. In this review, we summarize new antifungal targets and target-based inhibitor design, with a focus on their antifungal activity, selectivity, and mechanism. We also illustrate the prodrug design strategy used to improve the physicochemical and pharmacokinetic profiles of antifungal agents. Dual-targeting antifungal agents offer a new strategy for the treatment of resistant infections and cancer-associated fungal infections.
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Tharappel AM, Li Z, Zhu YC, Wu X, Chaturvedi S, Zhang QY, Li H. Calcimycin Inhibits Cryptococcus neoformans In Vitro and In Vivo by Targeting the Prp8 Intein Splicing. ACS Infect Dis 2022; 8:1851-1868. [PMID: 35948057 PMCID: PMC9464717 DOI: 10.1021/acsinfecdis.2c00137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Drug resistance is a significant concern in the treatment of diseases, including cryptococcosis caused by Cryptococcus neoformans (Cne) and Cryptococcus gattii (Cga). Alternative drug targets are necessary to overcome drug resistance before it attains a critical stage. Splicing of inteins from pro-protein precursors is crucial for activities of essential proteins hosting intein elements in many organisms, including human pathogens such as Cne and Cga. Through a high-throughput screening, we identified calcimycin (CMN) as a potent Prp8 intein splicing inhibitor with a minimum inhibitory concentration (MIC) of 1.5 μg/mL against the wild-type Cne-H99 (Cne-WT or Cne). In contrast, CMN inhibited the intein-less mutant strain (Cne-Mut) with a 16-fold higher MIC. Interestingly, Aspergillus fumigatus and a few Candida species were resistant to CMN. Further studies indicated that CMN reduced virulence factors such as urease activity, melanin production, and biofilm formation in Cne. CMN also inhibited Cne intracellular infection in macrophages. In a target-specific split nanoluciferase assay, the IC50 of CMN was 4.6 μg/mL. Binding of CMN to recombinant Prp8 intein was demonstrated by thermal shift assay and microscale thermophoresis. Treating Cne cells with CMN reduced intein splicing. CMN was fungistatic and showed a synergistic effect with the known antifungal drug amphotericin B. Finally, CMN treatment at 20 mg/kg body weight led to 60% reduction in lung fungal load in a cryptococcal pulmonary infection mouse model. Overall, CMN represents a potent antifungal with a novel mechanism of action to treat Cne and possibly Cga infections.
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Affiliation(s)
- Anil Mathew Tharappel
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Zhong Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Yan Chun Zhu
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Xiangmeng Wu
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
| | - Sudha Chaturvedi
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
| | - Qing-Yu Zhang
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
| | - Hongmin Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson Arizona 85721-0207, United States
- Wadsworth Center, New York State Department of Health, Albany, New York 12208, United States
- The BIO5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
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5
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Fernandes JAL, Zatti MDS, Arantes TD, de Souza MFB, Santoni MM, Rossi D, Zanelli CF, Liu XQ, Bagagli E, Theodoro RC. Cryptococcus neoformans Prp8 Intein: An In Vivo Target-Based Drug Screening System in Saccharomyces cerevisiae to Identify Protein Splicing Inhibitors and Explore Its Dynamics. J Fungi (Basel) 2022; 8:jof8080846. [PMID: 36012834 PMCID: PMC9410109 DOI: 10.3390/jof8080846] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/23/2022] [Accepted: 07/25/2022] [Indexed: 11/25/2022] Open
Abstract
Inteins are genetic mobile elements that are inserted within protein-coding genes, which are usually housekeeping genes. They are transcribed and translated along with the host gene, then catalyze their own splicing out of the host protein, which assumes its functional conformation thereafter. As Prp8 inteins are found in several important fungal pathogens and are absent in mammals, they are considered potential therapeutic targets since inhibiting their splicing would selectively block the maturation of fungal proteins. We developed a target-based drug screening system to evaluate the splicing of Prp8 intein from the yeast pathogen Cryptococcus neoformans (CnePrp8i) using Saccharomyces cerevisiae Ura3 as a non-native host protein. In our heterologous system, intein splicing preserved the full functionality of Ura3. To validate the system for drug screening, we examined cisplatin, which has been described as an intein splicing inhibitor. By using our system, new potential protein splicing inhibitors may be identified and used, in the future, as a new class of drugs for mycosis treatment. Our system also greatly facilitates the visualization of CnePrp8i splicing dynamics in vivo.
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Affiliation(s)
- José Alex Lourenço Fernandes
- Institute of Tropical Medicine, Federal University of Rio Grande do Norte (UFRN), Natal 59077-080, Rio Grande do Norte, Brazil
- Department of Biochemistry, Biosciences Center, Federal University of Rio Grande do Norte (UFRN), Natal 59078-900, Rio Grande do Norte, Brazil
- Ottawa Hospital Research Institute (OHRI), The University of Ottawa, Ottawa, ON K1H 8M5, Canada
- Correspondence: (J.A.L.F.); (R.C.T.)
| | - Matheus da Silva Zatti
- Institute of Tropical Medicine, Federal University of Rio Grande do Norte (UFRN), Natal 59077-080, Rio Grande do Norte, Brazil
- Department of Biochemistry, Biosciences Center, Federal University of Rio Grande do Norte (UFRN), Natal 59078-900, Rio Grande do Norte, Brazil
| | - Thales Domingos Arantes
- Department of Biosciences and Technology, Institute of Tropical Pathology and Public Health, Federal University of Goiás, Goiânia 74605-050, Goiás, Brazil
| | - Maria Fernanda Bezerra de Souza
- Department of Biochemistry, Biosciences Center, Federal University of Rio Grande do Norte (UFRN), Natal 59078-900, Rio Grande do Norte, Brazil
| | - Mariana Marchi Santoni
- School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara 14800-903, São Paulo, Brazil
| | - Danuza Rossi
- Pensabio, São Paulo 05005-010, São Paulo, Brazil
| | - Cleslei Fernando Zanelli
- School of Pharmaceutical Sciences, São Paulo State University (UNESP), Araraquara 14800-903, São Paulo, Brazil
| | - Xiang-Qin Liu
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
| | - Eduardo Bagagli
- Microbiology and Immunology Department, Biosciences Institute of Botucatu, São Paulo State University (UNESP), Botucatu 18618-689, São Paulo, Brazil
| | - Raquel Cordeiro Theodoro
- Institute of Tropical Medicine, Federal University of Rio Grande do Norte (UFRN), Natal 59077-080, Rio Grande do Norte, Brazil
- Correspondence: (J.A.L.F.); (R.C.T.)
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Wagner AG, Stagnitta RT, Xu Z, Pezzullo JL, Kandel N, Giner JL, Covey DF, Wang C, Callahan BP. Nanomolar, Noncovalent Antagonism of Hedgehog Cholesterolysis: Exception to the "Irreversibility Rule" for Protein Autoprocessing Inhibition. Biochemistry 2022; 61:1022-1028. [PMID: 34941260 PMCID: PMC9382716 DOI: 10.1021/acs.biochem.1c00697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hedgehog (Hh) signaling ligands undergo carboxy terminal sterylation through specialized autoprocessing, called cholesterolysis. Sterylation is brought about intramolecularly in a single turnover by an adjacent enzymatic domain, called HhC, which is found in precursor Hh proteins only. Previous attempts to identify antagonists of the intramolecular activity of HhC have yielded inhibitors that bind HhC irreversibly through covalent mechanisms, as is common for protein autoprocessing inhibitors. Here, we report an exception to the "irreversibility rule" for autoprocessing inhibition. Using a fluorescence resonance energy transfer-based activity assay for HhC, we screened a focused library of sterol-like analogues for noncovalent inhibitors and identified and validated four structurally related molecules, which were then used for structure-activity relationship studies. The most effective derivative, tBT-HBT, inhibits HhC noncovalently with an IC50 of 300 nM. An allosteric binding site for tBT-HBT, encompassing residues from the two subdomains of HhC, is suggested by kinetic analysis, mutagenesis studies, and photoaffinity labeling. The inhibitors described here resemble a family of noncovalent, allosteric inducers of HhC paracatalysis which we have described previously. The inhibition and the induction appear to be mediated by a shared allosteric site on HhC.
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Affiliation(s)
- Andrew G Wagner
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902, United States
| | - Robert T Stagnitta
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902, United States
| | - Zihan Xu
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902, United States
| | - John L Pezzullo
- Department of Chemistry, SUNY-ESF, Syracuse, New York 13210, United States
| | - Nabin Kandel
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180, United States
| | - José-Luis Giner
- Department of Chemistry, SUNY-ESF, Syracuse, New York 13210, United States
| | - Douglas F Covey
- Department of Developmental Biology, Taylor Family Institute for Innovative Psychiatric Research, 660 South Euclid Avenue, St. Louis, Missouri 63110, United States
| | - Chunyu Wang
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180, United States
| | - Brian P Callahan
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902, United States
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7
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Santos IA, Pereira AKDS, Guevara-Vega M, de Paiva REF, Sabino-Silva R, Bergamini FRG, Corbi PP, Jardim ACG. Repurposing potential of rimantadine hydrochloride and development of a promising platinum(II)-rimantadine metallodrug for the treatment of Chikungunya virus infection. Acta Trop 2022; 227:106300. [PMID: 34979144 DOI: 10.1016/j.actatropica.2021.106300] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 12/23/2021] [Accepted: 12/29/2021] [Indexed: 11/15/2022]
Abstract
Most of the patients infected with Chikungunya virus (CHIKV) develop chronic manifestations characterized by pain and deformity in joints, impacting their quality of life. The aminoadamantanes, in their turn, have been exploited due to their biological activities, with amantadine and memantine recently described with anti-CHIKV activities. Here we evaluated the antiviral activity of rimantadine hydrochloride (rtdH), a well-known antiviral agent against influenza A, its platinum complex (Pt-rtd), and the precursor cis-[PtCl2(dmso)2], against CHIKV infection in vitro. The rtdH demonstrated significant antiviral activity in all stages of CHIKV replication (29% in pre-treatment; 57% in early stages of infection; 60% in post-entry stages). The Pt-rtd complex protected the cells against infection in 92%, inhibited 100% of viral entry, mainly by a virucidal effect, and impaired 60% of post-entry stages. Alternatively, cis-[PtCl2(dmso)2] impaired viral entry in 100% and post-entry steps in 60%, but had no effect in protecting cells when administered prior to CHIKV infection. Collectively, the obtained data demonstrated that rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, with the strongest effect observed to Pt-rtd complex, which reduced up to 100% of CHIKV infection. Moreover, molecular docking analysis and infrared spectroscopy data (ATR-FTIR) suggest an interaction of Pt-rtd with CHIKV glycoproteins, potentially related to the mechanism of inhibition of viral entry by Pt-rtd. Through a migration retardation assay, it was also shown that Pt-rtd and cis-[PtCl2(dmso)2] interacted with the dsRNA in 87% and 100%, respectively. The obtained results highlight the repurposing potential of rtdH as an anti-CHIKV drug, as well as the synthesis of promising platinum(II) metallodrugs with potential application for the treatment of CHIKV infections. Importance Chikungunya fever is a disease that can result in persistent symptoms due to the chronic infection process. Infected patients can develop physical disability, resulting and high costs to the health system and significant impacts on the quality of life of affected individuals. Additionally, there are no licensed vaccines or antivirals against the Chikungunya virus (CHIKV) and the virus is easily transmitted due to the abundance of viable vectors in epidemic regions. In this context, our study highlights the repurposing potential of the commercial drug rimantadine hydrochloride (rtdH) as an antiviral agent for the treatment of CHIKV infections. Moreover, our data demonstrated that a platinum(II)-rimantadine metallodrug (Pt-rtd) poses as a potent anti-CHIKV molecule with potential application for the treatment of Chikungunya fever. Altogether, rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, reducing up to 100% of CHIKV infection in vitro.
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Affiliation(s)
- Igor Andrade Santos
- Laboratory of Virology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia-MG 38405-302, Brazil
| | | | - Marco Guevara-Vega
- Innovation Center in Salivary Diagnostic and Nanotheranostics, Department of Physiology, Institute of Biomedical Sciences, Federal University of Uberlandia, Minas Gerais, Brazil
| | | | - Robinson Sabino-Silva
- Innovation Center in Salivary Diagnostic and Nanotheranostics, Department of Physiology, Institute of Biomedical Sciences, Federal University of Uberlandia, Minas Gerais, Brazil
| | - Fernando R G Bergamini
- Laboratory of Synthesis of Bioinspired Molecules, Institute of Chemistry, Federal University of Uberlândia, Uberlândia-MG 34000-902, Brazil.
| | - Pedro P Corbi
- Institute of Chemistry, University of Campinas-UNICAMP, Campinas-SP 13083-871, Brazil.
| | - Ana Carolina G Jardim
- Laboratory of Virology, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia-MG 38405-302, Brazil; Institute of Biosciences, Humanities and Exact Sciences (Ibilce), São Paulo State University (Unesp), Campus São José do Rio Preto, São José do Rio Preto, São Paulo, Brazil.
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Tharappel AM, Li Z, Li H. Inteins as Drug Targets and Therapeutic Tools. Front Mol Biosci 2022; 9:821146. [PMID: 35211511 PMCID: PMC8861304 DOI: 10.3389/fmolb.2022.821146] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 01/10/2022] [Indexed: 12/12/2022] Open
Abstract
Multidrug-resistant pathogens are of significant concern in recent years. Hence new antifungal and anti-bacterial drug targets are urgently needed before the situation goes beyond control. Inteins are polypeptides that self-splice from exteins without the need for cofactors or external energy, resulting in joining of extein fragments. Inteins are present in many organisms, including human pathogens such as Mycobacterium tuberculosis, Cryptococcus neoformans, C. gattii, and Aspergillus fumigatus. Because intein elements are not present in human genes, they are attractive drug targets to develop antifungals and antibiotics. Thus far, a few inhibitors of intein splicing have been reported. Metal-ions such as Zn2+ and Cu2+, and platinum-containing compound cisplatin inhibit intein splicing in M. tuberculosis and C. neoformans by binding to the active site cysteines. A small-molecule inhibitor 6G-318S and its derivative 6G-319S are found to inhibit intein splicing in C. neoformans and C. gattii with a MIC in nanomolar concentrations. Inteins have also been used in many other applications. Intein can be used in activating a protein inside a cell using small molecules. Moreover, split intein can be used to deliver large genes in experimental gene therapy and to kill selected species in a mixed population of microbes by taking advantage of the toxin-antitoxin system. Furthermore, split inteins are used in synthesizing cyclic peptides and in developing cell culture model to study infectious viruses including SARS-CoV-2 in the biosafety level (BSL) 2 facility. This mini-review discusses the recent research developments of inteins in drug discovery and therapeutic research.
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Affiliation(s)
- Anil Mathew Tharappel
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Zhong Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
| | - Hongmin Li
- Department of Pharmacology and Toxicology, College of Pharmacy, The University of Arizona, Tucson, AZ, United States
- BIO5 Institute, The University of Arizona, Tucson, AZ, United States
- *Correspondence: Hongmin Li,
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Liu T, Pyle AM. Discovery of highly reactive self-splicing group II introns within the mitochondrial genomes of human pathogenic fungi. Nucleic Acids Res 2021; 49:12422-12432. [PMID: 34850132 PMCID: PMC8643640 DOI: 10.1093/nar/gkab1077] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/27/2021] [Accepted: 10/20/2021] [Indexed: 11/25/2022] Open
Abstract
Fungal pathogens represent an expanding global health threat for which treatment options are limited. Self-splicing group II introns have emerged as promising drug targets, but their development has been limited by a lack of information on their distribution and architecture in pathogenic fungi. To meet this challenge, we developed a bioinformatic workflow for scanning sequence data to identify unique RNA structural signatures within group II introns. Using this approach, we discovered a set of ubiquitous introns within thermally dimorphic fungi (genera of Blastomyces, Coccidioides and Histoplasma). These introns are the most biochemically reactive group II introns ever reported, and they self-splice rapidly under near-physiological conditions without protein cofactors. Moreover, we demonstrated the small molecule targetability of these introns by showing that they can be inhibited by the FDA-approved drug mitoxantrone in vitro. Taken together, our results highlight the utility of structure-based informatic searches for identifying riboregulatory elements in pathogens, revealing a striking diversity of reactive self-splicing introns with great promise as antifungal drug targets.
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Affiliation(s)
- Tianshuo Liu
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, 06520, USA
| | - Anna M Pyle
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT, 06520, USA.,Department of Chemistry, Yale University, New Haven, CT, 06520, USA.,Howard Hughes Medical Institute, Yale University, New Haven, CT, 06520, USA
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10
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Abstract
Intervening proteins, or inteins, are mobile genetic elements that are translated within host polypeptides and removed at the protein level by splicing. In protein splicing, a self-mediated reaction removes the intein, leaving a peptide bond in place. While protein splicing can proceed in the absence of external cofactors, several examples of conditional protein splicing (CPS) have emerged. In CPS, the rate and accuracy of splicing are highly dependent on environmental conditions. Because the activity of the intein-containing host protein is compromised prior to splicing and inteins are highly abundant in the microbial world, CPS represents an emerging form of posttranslational regulation that is potentially widespread in microbes. Reactive chlorine species (RCS) are highly potent oxidants encountered by bacteria in a variety of natural environments, including within cells of the mammalian innate immune system. Here, we demonstrate that two naturally occurring RCS, namely, hypochlorous acid (the active compound in bleach) and N-chlorotaurine, can reversibly block splicing of DnaB inteins from Mycobacterium leprae and Mycobacterium smegmatis in vitro. Further, using a reporter that monitors DnaB intein activity within M. smegmatis, we show that DnaB protein splicing is inhibited by RCS in the native host. DnaB, an essential replicative helicase, is the most common intein-housing protein in bacteria. These results add to the growing list of environmental conditions that are relevant to the survival of the intein-containing host and influence protein splicing, as well as suggesting a novel mycobacterial response to RCS. We propose a model in which DnaB splicing, and therefore replication, is paused when these mycobacteria encounter RCS. IMPORTANCE Inteins are both widespread and abundant in microbes, including within several bacterial and fungal pathogens. Inteins are domains translated within host proteins and removed at the protein level by splicing. Traditionally considered molecular parasites, some inteins have emerged in recent years as adaptive posttranslational regulatory elements. Several studies have demonstrated CPS, in which the rate and accuracy of protein splicing, and thus host protein functions, are responsive to environmental conditions relevant to the intein-containing organism. In this work, we demonstrate that two naturally occurring RCS, including the active compound in household bleach, reversibly inhibit protein splicing of Mycobacterium leprae and Mycobacterium smegmatis DnaB inteins. In addition to describing a new physiologically relevant condition that can temporarily inhibit protein splicing, this study suggests a novel stress response in Mycobacterium, a bacterial genus of tremendous importance to humans.
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11
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Wall DA, Tarrant SP, Wang C, Mills KV, Lennon CW. Intein Inhibitors as Novel Antimicrobials: Protein Splicing in Human Pathogens, Screening Methods, and Off-Target Considerations. Front Mol Biosci 2021; 8:752824. [PMID: 34692773 PMCID: PMC8529194 DOI: 10.3389/fmolb.2021.752824] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 09/24/2021] [Indexed: 01/20/2023] Open
Abstract
Protein splicing is a post-translational process by which an intervening polypeptide, or intein, catalyzes its own removal from the flanking polypeptides, or exteins, concomitant with extein ligation. Although inteins are highly abundant in the microbial world, including within several human pathogens, they are absent in the genomes of metazoans. As protein splicing is required to permit function of essential proteins within pathogens, inteins represent attractive antimicrobial targets. Here we review key proteins interrupted by inteins in pathogenic mycobacteria and fungi, exciting discoveries that provide proof of concept that intein activity can be inhibited and that this inhibition has an effect on the host organism's fitness, and bioanalytical methods that have been used to screen for intein activity. We also consider potential off-target inhibition of hedgehog signaling, given the similarity in structure and function of inteins and hedgehog autoprocessing domains.
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Affiliation(s)
- Diana A Wall
- Department of Chemistry, College of the Holy Cross, Worcester, MA, United States
| | - Seanan P Tarrant
- Department of Chemistry, College of the Holy Cross, Worcester, MA, United States
| | - Chunyu Wang
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States.,Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Kenneth V Mills
- Department of Chemistry, College of the Holy Cross, Worcester, MA, United States
| | - Christopher W Lennon
- Department of Biological Sciences, Murray State University, Murray, KY, United States
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12
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Possato B, Dalmolin LF, Pereira LM, Alves JQ, Silva RTC, Gelamo RV, Yatsuda AP, Lopez RFV, de Albuquerque S, Leite NB, Maia PIDS. Gold(III) complexes with thiosemicarbazonate ligands as potential anticancer agents: Cytotoxicity and interactions with biomolecular targets. Eur J Pharm Sci 2021; 162:105834. [PMID: 33826936 DOI: 10.1016/j.ejps.2021.105834] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 03/17/2021] [Accepted: 03/31/2021] [Indexed: 01/23/2023]
Abstract
Gold(III) complexes have been studied for the past years due to their anticancer properties and great affinity to biotargets, such as enzymes and proteins, which support their pharmacological applications. Within this scope, in this work the antiproliferative activities of two Au(III)-thiosemicarbazonate complexes, [AuClL1] (1, L1: (E,Z)-N-ethyl-N'-(3-nitroso-kN)butan-2-ylidene)carbamohydrazonothioato-k2N2,S) and [Au(Hdamp)L2]Cl (2, L2: N-(N'',N''-diethylaminothiocarbonyl)-N'(N''', N'''-dimethylcarbothioamide)benzamidineto-kN,k2S and Hdamp: 2-(N,N-dimethylaminomethyl)-phenyl-C1), and their affinities to possible biological targets were investigated. Three different tumor cell lines were used to perform the cytotoxicity assays, including one cisplatin-resistant model, and the results showed lower EC50 for 1 over 2 in every case: B16F10 (4.1 μM and 15.6 μM), A431 (4.0 μM and >50 μM) and OVCAR3 (4.2 μM and 24.5 μM). However, a lower toxicity to fibroblast 3T3 cell line was observed for 2 (30.58 μM) when compared to 1 (7.17 μM), resulting in comparable therapeutic indexes. Both complexes presented strong affinity to HSA: they distorted the secondary structure of the protein, as verified by circular dichroism, but 1 additionally presented the apparent fluorescence quenching constant (Kapp) ten times greater than 2, which was probably due to the fact of 1 being able to denature HSA. The ethidium bromide displacement assay showed that neither 1 nor 2 are strong DNA intercalators, which is in agreement with what was observed through the UV-vis titration. In both cases, the 260 nm band presented hyperchromism, which can indicate ionic interactions or DNA damage. In fact, 1 was able to damage the pGEM plasmid, similarly to cisplatin, as verified by agarose gel electrophoresis and Atomic Force Microscopy. Biophysical studies in cancer cells model membranes were also performed in order to investigate the interaction of the gold complexes to lipid bilayers and revealed that the compounds interact with the membranes by exhibiting partition coefficients of 103 order of magnitude. Overall, both complexes were found to be promising candidates for the development of a future anticancer drug against low sensitive or cisplatin resistant tumors.
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Affiliation(s)
- Bruna Possato
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Luciana Falcco Dalmolin
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Luiz Miguel Pereira
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | | | | | - Rogerio Valentim Gelamo
- Instituto de Ciências Tecnológicas e Exatas, Universidade Federal do Triângulo Mineiro, Uberaba, Brazil
| | - Ana Patrícia Yatsuda
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | | | - Sérgio de Albuquerque
- Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Natália Bueno Leite
- Núcleo de Desenvolvimento de Compostos Bioativos (NDCBio), Universidade Federal do Triângulo Mineiro, Uberaba, Brazil.
| | - Pedro Ivo da Silva Maia
- Núcleo de Desenvolvimento de Compostos Bioativos (NDCBio), Universidade Federal do Triângulo Mineiro, Uberaba, Brazil.
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13
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Woods D, LeSassier DS, Egbunam I, Lennon CW. Construction and Quantitation of a Selectable Protein Splicing Sensor Using Gibson Assembly and Spot Titers. Curr Protoc 2021; 1:e82. [PMID: 33739627 DOI: 10.1002/cpz1.82] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Inteins (intervening proteins) are translated within host proteins and removed through protein splicing. Conditional protein splicing (CPS), where the rate and accuracy of splicing are highly dependent on environmental cues, has emerged as a novel form of post-translational regulation. While CPS has been demonstrated for several inteins in vitro, a comprehensive understanding of inteins requires tools to quantitatively monitor their activity within the cellular context. Here, we describe a method for construction of a splicing-dependent system that can be used to quantitatively assay for conditions that modulate protein splicing. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Construction of an intein-containing KanR2 library using Gibson assembly Basic Protocol 2: Phenotype determination using quantitative spot titers Support Protocol 1: Preparation of LB agar plates for spot titers Support Protocol 2: Preparation and transformation of competent M. smegmatis cells.
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Affiliation(s)
- Daniel Woods
- Wadsworth Center, New York State Department of Health, Albany, New York
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14
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Panda S, Nanda A, Nasker SS, Sen D, Mehra A, Nayak S. Metal effect on intein splicing: A review. Biochimie 2021; 185:53-67. [PMID: 33727137 DOI: 10.1016/j.biochi.2021.03.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 03/04/2021] [Accepted: 03/06/2021] [Indexed: 02/08/2023]
Abstract
Inteins are intervening polypeptides that interrupt the functional domains of several important proteins across the three domains of life. Inteins excise themselves from the precursor protein, ligating concomitant extein residues in a process called protein splicing. Post-translational auto-removal of inteins remain critical for the generation of active proteins. The perspective of inteins in science is a robust field of research, however fundamental studies centralized upon splicing regulatory mechanism are imperative for addressing more intricate issues. Controlled engineering of intein splicing has many applications; intein inhibition can facilitate novel drug design, while activation of intein splicing is exploited in protein purification. This paper provides a comprehensive review of the past and recent advances in the splicing regulation via metal-intein interaction. We compare the behavior of different metal ions on diverse intein systems. Though metals such as Zn, Cu, Pt, Cd, Co, Ni exhibit intein inhibitory effect heterogeneously on different inteins, divalent metal ions such as Ca and Mg fail to do so. The observed diversity in the metal-intein interaction arises mostly due to intein polymorphism and variations in atomic structure of metals. A mechanistic understanding of intein regulation by metals in native as well as synthetically engineered intein systems may yield potent intein inhibitors via direct or indirect approach.
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Affiliation(s)
- Sunita Panda
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Ananya Nanda
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Sourya Subhra Nasker
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Debjani Sen
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Ashwaria Mehra
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India
| | - Sasmita Nayak
- School of Biotechnology, Kalinga Institute of Industrial Technology, Bhubaneswar, Odisha, 751024, India.
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15
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Abstract
Self-splicing proteins, called inteins, are present in many human pathogens, including the emerging fungal threats Cryptococcus neoformans (Cne) and Cryptococcus gattii (Cga), the causative agents of cryptococcosis. Inhibition of protein splicing in Cryptococcus sp. interferes with activity of the only intein-containing protein, Prp8, an essential intron splicing factor. Here, we screened a small-molecule library to find addititonal, potent inhibitors of the Cne Prp8 intein using a split-GFP splicing assay. This revealed the compound 6G-318S, with IC50 values in the low micromolar range in the split-GFP assay and in a complementary split-luciferase system. A fluoride derivative of the compound 6G-318S displayed improved cytotoxicity in human lung carcinoma cells, although there was a slight reduction in the inhibition of splicing. 6G-318S and its derivative inhibited splicing of the Cne Prp8 intein in vivo in Escherichia coli and in C. neoformans Moreover, the compounds repressed growth of WT C. neoformans and C. gattii In contrast, the inhibitors were less potent at inhibiting growth of the inteinless Candida albicans Drug resistance was observed when the Prp8 intein was overexpressed in C. neoformans, indicating specificity of this molecule toward the target. No off-target activity was observed, such as inhibition of serine/cysteine proteases. The inhibitors bound covalently to the Prp8 intein and binding was reduced when the active-site residue Cys1 was mutated. 6G-318S showed a synergistic effect with amphotericin B and additive to indifferent effects with a few other clinically used antimycotics. Overall, the identification of these small-molecule intein-splicing inhibitors opens up prospects for a new class of antifungals.
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16
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Kim JH, Cheng LW, Chan KL, Tam CC, Mahoney N, Friedman M, Shilman MM, Land KM. Antifungal Drug Repurposing. Antibiotics (Basel) 2020; 9:antibiotics9110812. [PMID: 33203147 PMCID: PMC7697925 DOI: 10.3390/antibiotics9110812] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/30/2020] [Accepted: 11/13/2020] [Indexed: 12/19/2022] Open
Abstract
Control of fungal pathogens is increasingly problematic due to the limited number of effective drugs available for antifungal therapy. Conventional antifungal drugs could also trigger human cytotoxicity associated with the kidneys and liver, including the generation of reactive oxygen species. Moreover, increased incidences of fungal resistance to the classes of azoles, such as fluconazole, itraconazole, voriconazole, or posaconazole, or echinocandins, including caspofungin, anidulafungin, or micafungin, have been documented. Of note, certain azole fungicides such as propiconazole or tebuconazole that are applied to agricultural fields have the same mechanism of antifungal action as clinical azole drugs. Such long-term application of azole fungicides to crop fields provides environmental selection pressure for the emergence of pan-azole-resistant fungal strains such as Aspergillus fumigatus having TR34/L98H mutations, specifically, a 34 bp insertion into the cytochrome P450 51A (CYP51A) gene promoter region and a leucine-to-histidine substitution at codon 98 of CYP51A. Altogether, the emerging resistance of pathogens to currently available antifungal drugs and insufficiency in the discovery of new therapeutics engender the urgent need for the development of new antifungals and/or alternative therapies for effective control of fungal pathogens. We discuss the current needs for the discovery of new clinical antifungal drugs and the recent drug repurposing endeavors as alternative methods for fungal pathogen control.
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Affiliation(s)
- Jong H. Kim
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA; (L.W.C.); (K.L.C.); (C.C.T.); (N.M.)
- Correspondence: ; Tel.: +1-510-559-5841
| | - Luisa W. Cheng
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA; (L.W.C.); (K.L.C.); (C.C.T.); (N.M.)
| | - Kathleen L. Chan
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA; (L.W.C.); (K.L.C.); (C.C.T.); (N.M.)
| | - Christina C. Tam
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA; (L.W.C.); (K.L.C.); (C.C.T.); (N.M.)
| | - Noreen Mahoney
- Foodborne Toxin Detection and Prevention Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA; (L.W.C.); (K.L.C.); (C.C.T.); (N.M.)
| | - Mendel Friedman
- Healthy Processed Foods Research Unit, Western Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Albany, CA 94710, USA;
| | | | - Kirkwood M. Land
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA;
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17
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Woods D, Vangaveti S, Egbanum I, Sweeney AM, Li Z, Bacot-Davis V, LeSassier DS, Stanger M, Hardison GE, Li H, Belfort M, Lennon CW. Conditional DnaB Protein Splicing Is Reversibly Inhibited by Zinc in Mycobacteria. mBio 2020; 11:e01403-20. [PMID: 32665276 PMCID: PMC7360933 DOI: 10.1128/mbio.01403-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 06/09/2020] [Indexed: 11/20/2022] Open
Abstract
Inteins, as posttranslational regulatory elements, can tune protein function to environmental changes by conditional protein splicing (CPS). Translated as subdomains interrupting host proteins, inteins splice to scarlessly join flanking sequences (exteins). We used DnaB-intein1 (DnaBi1) from a replicative helicase of Mycobacterium smegmatis to build a kanamycin intein splicing reporter (KISR) that links splicing of DnaBi1 to kanamycin resistance. Using expression in heterologous Escherichia coli, we observed phenotypic classes of various levels of splicing-dependent resistance (SDR) and related these to the insertion position of DnaBi1 within the kanamycin resistance protein (KanR). The KanR-DnaBi1 construct demonstrating the most stringent SDR was used to probe for CPS of DnaB in the native host environment, M. smegmatis We show here that zinc, important during mycobacterial pathogenesis, inhibits DnaB splicing in M. smegmatis Using an in vitro reporter system, we demonstrated that zinc potently and reversibly inhibited DnaBi1 splicing, as well as splicing of a comparable intein from Mycobacterium leprae Finally, in a 1.95 Å crystal structure, we show that zinc inhibits splicing through binding to the very cysteine that initiates the splicing reaction. Together, our results provide compelling support for a model whereby mycobacterial DnaB protein splicing, and thus DNA replication, is responsive to environmental zinc.IMPORTANCE Inteins are present in a large fraction of prokaryotes and localize within conserved proteins, including the mycobacterial replicative helicase DnaB. In addition to their extensive protein engineering applications, inteins have emerged as environmentally responsive posttranslational regulators of the genes that encode them. While several studies have shown compelling evidence of conditional protein splicing (CPS), examination of splicing in the native host of the intein has proven to be challenging. Here, we demonstrated through a number of measures, including the use of a splicing-dependent sensor capable of monitoring intein activity in the native host, that zinc is a potent and reversible inhibitor of mycobacterial DnaB splicing. This work also expands our knowledge of site selection for intein insertion within nonnative proteins, demonstrating that splicing-dependent host protein activation correlates with proximity to the active site. Additionally, we surmise that splicing regulation by zinc has mycobacteriocidal and CPS application potential.
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Affiliation(s)
- Daniel Woods
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | - Sweta Vangaveti
- The RNA Institute, University at Albany, Albany, New York, USA
| | - Ikechukwu Egbanum
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | - Allison M Sweeney
- Department of Biology, Murray State University, Murray, Kentucky, USA
| | - Zhong Li
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Valjean Bacot-Davis
- Renaissance School of Medicine, Stony Brook University, Stony Brook, New York, USA
| | | | - Matthew Stanger
- Department of Biological Sciences, University at Albany, Albany, New York, USA
| | | | - Hongmin Li
- Department of Biological Sciences, University at Albany, Albany, New York, USA
- Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Marlene Belfort
- Department of Biological Sciences, University at Albany, Albany, New York, USA
- The RNA Institute, University at Albany, Albany, New York, USA
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18
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Green CM, Li Z, Smith AD, Novikova O, Bacot-Davis VR, Gao F, Hu S, Banavali NK, Thiele DJ, Li H, Belfort M. Spliceosomal Prp8 intein at the crossroads of protein and RNA splicing. PLoS Biol 2019; 17:e3000104. [PMID: 31600193 PMCID: PMC6805012 DOI: 10.1371/journal.pbio.3000104] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 10/22/2019] [Accepted: 09/13/2019] [Indexed: 01/07/2023] Open
Abstract
The spliceosome is a large ribonucleoprotein complex that removes introns from pre-mRNAs. At its functional core lies the essential pre-mRNA processing factor 8 (Prp8) protein. Across diverse eukaryotes, this protein cofactor of RNA catalysis harbors a self-splicing element called an intein. Inteins in Prp8 are extremely pervasive and are found at 7 different sites in various species. Here, we focus on the Prp8 intein from Cryptococcus neoformans (Cne), a human fungal pathogen. We solved the crystal structure of this intein, revealing structural homology among protein splicing sequences in eukaryotes, including the Hedgehog C terminus. Working with the Cne Prp8 intein in a reporter assay, we find that the biologically relevant divalent metals copper and zinc inhibit intein splicing, albeit by 2 different mechanisms. Copper likely stimulates reversible modifications on a catalytically important cysteine, whereas zinc binds at the terminal asparagine and the same critical cysteine. Importantly, we also show that copper treatment inhibits Prp8 protein splicing in Cne. Lastly, an intein-containing Prp8 precursor model is presented, suggesting that metal-induced protein splicing inhibition would disturb function of both Prp8 and the spliceosome. These results indicate that Prp8 protein splicing can be modulated, with potential functional implications for the spliceosome.
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Affiliation(s)
- Cathleen M. Green
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America
| | - Zhong Li
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Aaron D. Smith
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Olga Novikova
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America
| | - Valjean R. Bacot-Davis
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America
| | - Fengshan Gao
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Saiyang Hu
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Nilesh K. Banavali
- Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America,Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
| | - Dennis J. Thiele
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina, United States of America,Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, North Carolina, United States of America,Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina, United States of America
| | - Hongmin Li
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America,Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America,* E-mail: (MB); (HL)
| | - Marlene Belfort
- Department of Biological Sciences and RNA Institute, University at Albany, Albany, New York, United States of America,Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America,* E-mail: (MB); (HL)
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